# Copyright 2021 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the License);
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# Copyright (c) Open-MMLab. All rights reserved.
from ..dist_utils import allreduce_params
from .hook import HOOKS, Hook


@HOOKS.register_module()
class SyncBuffersHook(Hook):
    """Synchronize model buffers such as running_mean and running_var in BN at
    the end of each epoch.

    Args:
        distributed (bool): Whether distributed training is used. It is
          effective only for distributed training. Defaults to True.
    """

    def __init__(self, distributed=True):
        self.distributed = distributed

    def after_epoch(self, runner):
        """All-reduce model buffers at the end of each epoch."""
        if self.distributed:
            allreduce_params(runner.model.buffers())
